1. Field of the Invention
The present invention relates to an image processing apparatus and method suitable for performing a filtering process and coding process of image data, and to a computer readable storage medium storing process for realizing such a method.
2. Relata Background Art
Digital still cameras are widely used as an image pickup device for computers. An image compression method utilizing DCT (discrete cosine transform) such as JPEG is used for digital still cameras. While digital still cameras are prevailing, high speed continuous photographing and power saving have been desired. In order to shorten the time taken to pickup images and record image data, the processes from signal processing to image compression have been conducted heretofore by hardware.
With a conventional hardware configuration, a capacity proportional to the input image scan size in a horizontal direction is required for a buffer which is used for filtering accumulated charge information read from image pickup elements such as CCD in horizontal and vertical directions and for a buffer which is used for raster/block conversion of raster scan sequential image data into block scan sequential image data. For example, assuming that input image data has 1034 pixels in the horizontal direction and 770 pixels in the vertical direction, a horizontal filter has 11 taps, a vertical filter has 3 taps, a YUV sampling ratio of JPEG is 4:2:2, CCD image data has 10 bits, and each of YUV has 8 bits, the following data is determined:
Hd=1034, where Hd is the number of pixels of input image data in the horizontal direction;
Hr=1034xe2x88x92INT(11/2)xc3x972=1024, where Hr is the number of pixels of image data in the horizontal direction output after signal processing (a filtering process, a YC separation, an edge process, a gamma process, and the like);
a capacity of a buffer for filtering in the horizontal and vertical directions =2xc3x97Hdxc3x9710=20680 (bits); and
a capacity of a buffer for raster/block conversion=8xc3x97Hr ((the number of bits of Y) +(the number of bits of UV)) =8xc3x971024xc3x9716=131072 (bits).
In the system using a plurality of image sizes, the buffer capacity has been determined conventionally in accordance with a maximum horizontal image size, respectively for a buffer for filtering in the horizontal and vertical directions and for a buffer for raster/block conversion. This is not economical.
Conventional techniques are associated with a problem that when a CCD sensor of non-square is used, the compressed image data has distortion.
There is also a problem that since image data after signal processing is JPEG compressed, it is difficult to resize the image data.
Under the above-described background of the invention, it is an object of the present invention to provide an image processing apparatus and method capable of processing image data having an arbitrary size at high speed independently from the capacity of a buffer memory, and a computer readable storage medium storing processes realizing such a method.
In order to achieve the above object of the invention, according to one aspect of the present invention, there is provided an image processing apparatus/method wherein input image data is divided into blocks adjacent blocks of which partially overlap the image data, and the divided image data is subject to a filtering process in a block unit basis.
According to an another aspect of the present invention, there is provided readable storage medium which stores a program executing steps of inputting image data and dividing the input image data into blocks adjacent blocks of which partially overlap the image data.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.